Collectorless direct current motor, driver circuit for a drive and method of operating a collectorless direct current motor

ABSTRACT

A method for the low-loss regulation of a collectorless direct current motor and a semiconductor circuit has, during the commutation phase given by a position sensor and with reduced motor output and number of revolutions, transistors or one end transistor which initially operates temporarily as a switch and thereafter operates temporarily as an analog amplifier element. During the analog period, a current is available which changes slowly according to a ramp function.

This application is a continuation of reissue application Ser. No.07/654,493, filed Feb. 13, 1991, now U.S. Pat. No. RE 34,609, which is areissue application of application Ser. No. 07/072,264, filed Jun. 22,1987, now U.S. Pat. No. 4,804,892.

BACKGROUND OF THE INVENTION

The present invention relates to a collectorless direct current motorequipped with a fan or for driving a fan and including a permanentmagnet rotor in the field of at least one stator winding and to a methodof operating such a motor. In particular, the invention relates to adriver circuit for a collectorless direct current motor including apermanent magnet rotor having at least two poles and at least one statorwinding connected to the driver circuit end stage which temporarilyoperates as a switch and a sensor detecting the position of the rotor,with the control signal fed to the end stage during each commutationphase causing the current in the stator winding to have a ramp-shapedconfiguration.

Such a driver circuit is disclosed in No. DE-OS 3,107,623 and includesan RC member with the aid of which rectangular signals are reshaped tocontrol the direct current motor in order to reduce the steepness oftheir edges, thus reducing the winding noise of the motor. However, inthe known driver circuit, there exists neither a possibility to changethe number of revolutions nor a possibility to regulate the number ofrevolutions as a function of an external physical value independently ofthe operating voltage.

It is known to detect the position of the rotor by means of at least onegalvanomagnetic element, a Hall generator or the like, and to use thesignal generated in this element, which is a function of the rotorposition, to control, by way of semiconductor elements, the currents inone or a plurality of stator windings.

The control circuits employed for this purpose are supplemented bymembers which regulate the number of revolutions as a function ofexternally detectable physical values with an otherwise constantoperating voltage. Regulation of the number of revolutions may becontrolled as a function of various parameters or it may involve anadjustment of the number of revolutions of a fan driving motor whichprovides ventilation that is automatically adapted to demands for astream of air. In this case, the fan may be part of a device to becooled which heats up to different temperatures and whose heat is to bedissipated by the fan. In that case, the heat to be dissipated would bethe external physical command variable which determines the regulationof the number of revolutions.

Not only for this exemplary case of use but quite generally, users ormanufacturers of such direct current drives desire to make available thesmallest possible motors for their space-saving advantages. Power lossesshould be kept low.

To vary the output of motors operated with a constant operating voltage,it is known to pulse width modulate the motor current. In this case, alow pulse frequency in the audible frequency range is selected. Such afrequency does not produce much additional power loss and does notradiate much interference onto adjacent devices, but it does have thedrawback of developing a considerable amount of additional noise.Therefore it is also known to select a high pulse frequency in order toreduce noise. Then, stray high frequency fields result which interferewith the devices with which the fans and the corresponding directcurrent drives are associated. The simplest regulation employs a roughturn-on and turn-off range with the drawback of restless, rumbling motoroperation. The demand for small structures gives rise to the additionaldesire to integrate the components employed in the circuits and tocombine them in a chip. Therefore, the power losses in the integratedactive and passive components employed must be kept low so that thecomponents can be placed in close, juxtaposition and encapsulated. Thisdemand is counter to the necessity of allowing sufficient current toflow in the electromagnetic peaks then occur in the control circuits andthe heat generated by these peaks must not be permitted to destroy theintegrated electronic components.

SUMMARY OF THE INVENTION

It is an object of the invention to make available a driver circuit fora collectorless direct current motor so as to permit changes in outputpower and number of revolutions with small amounts of circuitry and at aconstant operating voltage; power losses in the components should below, particularly in the semiconductor paths and here again particularlyin the amplifying semiconductor paths, e.g. the end stage transistors.Moreover, additional motor noise and stray high frequency interferencesshould be kept low.

To solve these problems it is proposed, in general, to permit the activecomponents, i.e. inserted semiconductor paths, to act differently in thesame circuit in dependence on given external conditions or externalphysical command variables. For example, some of the semiconductorelements for controlling the currents for the stator winding or windingsmay operate as analog amplifier elements and, near the maximum possiblenumber of revolutions, as switches, to thus shorten the turn-onduration, for example, during a commutation phase. As one feature ofthis solution, ramp-shaped current curves can be generated in thecircuit over time, along which the switch positions may be varied.Another possible solution can be realized by means of a delay circuitwhich delays the moment of turn-on given by the position detector as afunction of the external command variable.

As a whole, the invention is based on the idea of avoiding power lossesin all components. Thus it becomes possible to integrate the components.The external conditions for the different operating states are detectedby at least one component. It is known to employ temperature sensitivecomponents in a ventilation stream to regulate the number of revolutionsor power of a collectorless direct current motor used in conjunctionwith 9 a fan. This, however, is effected by directly setting the poweroutput in the end stage semiconductors. Although this does not produceany additional high frequency fields which could interfere with thedevices to be ventilated and such a regulation does not produce anyadditional noise, a considerable amount of additional power lossdevelops in the partial load range concomitant with heating of thesemiconductor paths. This heating is an impediment for integration ofthe components. The present invention is based on the realization that,over long “on” periods, these motors are driven only in the partial loadrange. According to the invention, the motor current is thereforeregulated within this range, for example by way of pulse widthmodulation with a frequency equal to the commutation frequency of themotor and by operating the actuated end stage semiconductor within oneturn-on phase as a switch and subsequently in an analog mode. Duringthis analog operation, the motor current can be reduced, for example,according to a ramp function generated in the driver circuit.

The combination of switch operation and analog operation, preferably inconnection with a low rate of revolution at synchronous switchingfrequencies, permits a significant reduction of the losses in thesemiconductor paths and also of electromagnetic and acousticinterferences.

As a further feature of the present invention, the instant at which themotor current is turned on, when the motor is under partial load, isdelayed with respect to the turn-on instant which is indicated by aposition indicator. This produces a further smoothing of motoroperation. Evidently two effects are here at work. The generation of aparasitic axial force which has its maximum in the commutation range isreduced. Secondly, the counter-emf which rises rapidly after thetheoretical moment of communutation now considerably reduces the currentrise rate so that in spite of pure switch operation, the currentincreases relatively slowly.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, aspects, configurations and advantages of theinvention will become evident from the claims and the description belowof embodiments which are illustrated in the drawing figures.

FIG. 1 shows a block circuit diagram to illustrate the basic function ofa driver circuit according to the invention;

FIG. 2 shows a block circuit diagram for a first embodiment of thedriver circuit according to the invention;

FIG. 3 shows a circuit for a dual-pulse, two-wire, collectorless directcurrent motor with or without reluctance moment in which the number ofrevolutions is regulated as a function of an external physical valuewithout an internal auxiliary value;

FIG. 4 shows an embodiment modified, compared to FIG. 3, with respect tothe initiation of a control voltage;

FIG. 5 shows a circuit example including an additional control voltagegenerated across the stator coils;

FIG. 6 shows a modified embodiment compared to FIG. 5;

FIG. 7 shows a first simple embodiment including a generator inserted togenerate a ramp edge;

FIG. 8 shows a modified embodiment for generating the ramp edge;

FIG. 9 shows a further modified embodiment of FIG. 8; and

FIG. 10 shows a further modified embodiment of an inserted sawtoothgenerator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The block circuit diagram shown in FIG. 1 shows a driver circuit for acollectorless direct current motor including a first stator winding 100and a second stator winding 110. Stator windings 100, 110 are connected,with their one winding end, to a first terminal 10 to supply theoperating voltage for the collectorless direct current motor. Firststator winding 100 lies in the collector circuit of a power transistor60 of the driver circuit while second stator winding 110 lies in thecollector circuit of a power transistor 70. The emitters of powertransistors 60, 70, which form the end stage of the driver circuit, areconnected, via a feedback resistor 1, with a second terminal 12 for theoperating voltage. By alternatingly periodically actuating powertransistors 60 and 70, magnetic fields are generated alternatingly bystator windings 100, 110 to cause the permanent magnet rotor of thecollectorless direct current motor to rotate.

The continuous rotary position of the rotor (not shown in the drawing)of the direct current motor is detected with the aid of a sensor circuit2 which may contain, for example, a Hall element associated with anamplifier and a pulse shaping member. Corresponding to the rotation ofthe rotor, pulse-shaped periodic sensor signals 5, 6 offset by 180°appear at outputs 3, 4. The negative edges 7 of pulse-shaped sensorsignals 5 lie, in time, shortly before the positive edges 8 ofpulse-shaped sensor signals 6. Correspondingly, the negative edges 7 ofsensor signal 6 lie, in time, shortly before the positive edges 8 ofsensor signal 5.

As can be seen in FIG. 1, the periodic sensor signals 5, 6 do notdirectly actuate power transistors 60, 70 as is the case in conventionaldriver circuits for collectorless direct current motors.

As can be seen in FIG. 1, outputs 3, 4 of sensor circuit 2 are connectedwith control inputs 9, 11 of a linkage circuit 13. Linkage circuit 13makes it possible to apply an end stage control signal 19 present atinput 15 of linkage circuit 13 selectively to the base of powertransistor 60 or to the base of power transistor 70 in dependence on thesignals at control inputs 9, 11. Linkage circuit 13 fixes a time framefor actuation of power transistors 60, 70 corresponding to thecommutation periods of the direct current motor, with such time framebeing defined by the closed position of switches 17, 18 whichsymbolically represent linkage circuit 13. If, for example, controlinput 9 is charged by a positive edge of sensor signal 5, switch 17closes so that the end stage control signal 19 present at input 15 oflinkage circuit 13 is able to reach the base of power transistor 60. Ifthe negative edge appears, switch 17 opens and end stage control signal19 is prevented from acting on power transistor 60. However, as soon asswitch 18 of linkage circuit 13 is closed via control input 11, endstage control signal 19 reaches power transistor 70.

The driver circuit according to FIG. 1 is configured in such a way thatthe pulses of the likewise pulse-shaped end stage control signal 19 areless in duration than the pulses of sensor signals 5, 6. In this way itis possible to effect the actuation of power transistors 60, 70 eachtime only within part of the time frame given by the pulses of sensorsignals 5, 6. If the respective pulses present at input 15 becomeshorter compared to the pulses present at control inputs 9, 11, thetimes during which current flows through power transistors 60, 70 andstator windings 100, 110 become shorter. The pulse lengths in end stagecontrol signal 19 thus permit influencing the torque and/or the numberof revolutions of the collectorless direct current motor. Moreover, thesignal shape of the pulses of end stage control signal 19 can bedesigned in such a manner that the leading and/or trailing edges of thecurrents flowing through stator windings 100, 110 become flatter,keeping motor noise and power losses in power transistors 60, 70 as lowas possible.

According to the block circuit diagram shown in FIG. 1, end stagecontrol signal 19 is generated by a ramp generator 21 which isconnected, via two control inputs 23, 25, with outputs 3, 4 of sensorcircuit 2. Ramp generator 21 is, for example, a sawtooth or deltavoltage generator which makes available at its output 29 a delta voltage31 whose frequency is double the frequency of sensor signals 5, 6.

Between output 29 of ramp generator 21 and input 15 of linkage circuit13 lies a pulse width shaper 32. Pulse width shaper 32 includes acomparison amplifier circuit, abbreviatedly called comparator 33 whichreceives the delta voltage signal 31 at its first input 34 and theoutput signal of a number of revolutions setting circuit 36 at itssecond input 35. The output signal of number of revolutions settingcircuit 36 serves to preset a threshold value in such a manner that asignal appears at output 37 whenever delta voltage 31 lies above therespectively set threshold value. In this way, output 37 furnishes anend stage control signal 19 of delta voltage pulses whose maximumamplitude and whose base lengths are dependent on the signal at thesecond input 35 of comparator 33. If, for example, number of revolutionssetting circuit 36 sets a lower threshold value, the edges of end stagecontrol signal 19 approach one another in that the pulse shape of endstage control signal 19 approximates the pulse shape of delta voltage31, with the base length of the pulses and their maximum amplitude atthe delta voltage peaks becoming greater.

If end stage control signal 19 reaches power transistors 60, 70 withdelta pulses which are spaced at a greater distance from one another,the current through stator windings 100, 110 increases corresponding tothe increasing delta edges. In this case, power transistors 60, 70switch through completely only if end stage control signals 19 exceed anamplitude given by the respective circuit and the impedance of statorwindings 100, 110. Until this switching state is reached, powertransistors 60, 70 operate in the analog mode. After power transistors60, 70 have switched, the current curve through stator windings 100, 110changes only slightly until, finally, the descending edges actuate aslower current drop in end stage control signal 19.

The change in amplitude of the output signal of a revolution ratesetting circuit 3 36thus makes it possible to vary the pulse lengths bymeans of stator windings 100, 110 within the time frame for setting thenumber of revolutions as given by sensor signals 5, 6.

If it is desired to regulate the revolution rate in a closed controlcircuit, a revolution rate sensor 38 may be provided as likewise shownin FIG. 1, which converts the number of revolutions n per unit time ofthe direct current motor into a direct voltage U which travels through aline 39 to the revolution rate setting circuit 36. It is then possibleto set a revolution rate which is monitored with the aid of the sensor38 and causes the revolution rate to be adjusted by a change in theoutput signal of the setting circuit 36, for example, if the revolutionrate drops due to a greater motor load.

FIG. 2 shows exemplary embodiments to clarify some details of the blockcircuit diagram shown in FIG. 1 for a driver circuit according to theinvention. Components already known from FIG. 1 bear the same referencenumerals. The driver circuit according to the embodiment shown in FIG. 2likewise serves to actuate dual pulse, two-wire, collectorless directcurrent motors. A change in torque and/or revolution rate of the directcurrent motor is effected by changing the ratio of duration of turn-onto turn-off within each commutation period associated with theabove-mentioned time frame. Switching of the motor current thereforetakes place “gently” in order to suppress as much as possible anyswitching noises and high frequency interferences. For that reason,power transistors 60, 70 operate temporarily as linear amplifiers duringturn-on and turn-off, respectively, and gradually change the currentflowing through stator windings 100, 110 according to a given rampfunction having a constant edge slope. In a manner to be describedbelow, the number of revolutions of the direct current motor isregulated with the use of the voltage induced in stator windings 100,110 by means of a simple power controller. The command variable for therevolution rate is the applied operating voltage to which the revolutionrate is approximately proportional and, if desired, the ambienttemperature which is detected with the aid of a measuring sensorincluding a temperature-dependent resistor 51, for example an NTCresistor.

According to the embodiment shown in FIG. 2, the sensor circuit knownfrom FIG. 1 includes a Hall generator 260, whose first control input isconnected to terminal 12 and whose second control input is connected,via a resistor 52 and a device 53 providing thermal overload protection,to the operating voltage supplied through terminal 10 and a diode 14.The device 53 providing thermal overload protection includes amonitoring circuit for the temperature of power transistors 60, 70, soas to ensure turn-off with hystresis if the permissible transition zonetemperature of power transistors 60, 70 is exceeded.

Hall generator 260 furnishes voltages proportional to the magnetic fieldof the direct current motor and these voltages are amplified viacomparators 54 and 55 in order to generate the sensor signals 5, 6 shownschematically in FIG. 1. The pulse-shaped sensor signals 5, 6 are fed,on the one hand, to a linkage circuit formed of transistors 56, 57 and,on the other hand, to ramp generator 21. The effect of transistors 56and 57 corresponds to switches 17 and 18 shown in FIG. 1.

Ramp generator 21 is configured as a delta voltage generator including acontrol input 58 connected with the first output 61 of a currentgenerator 67 which has a second output 63 and a third output 65 and isconnected with three controlled current sources 71, 72 and 73. Currentsources 71, 72, 73 are controlled via a smoothed direct voltage whichappears at output 74 of a lowpass filter 75 whose input 76 is connected,via a resistor 77 and diodes 78, 79, with the transistor side ends ofstator windings 100, 110. By way of diodes 78, 79, a voltage induced instator windings 100, 110 which constitutes a measure of the number ofrevolutions, reaches lowpass filter 75 which, in addition to a filtercapacitor 80, includes an external fixed resistor 81 so as to make thevoltage/current conversion independent of the absolute tolerances of theinternal resistances. Since the driver circuit shown in FIG. 2 isrealized as an integrated circuit, several stages are provided withterminals for external connections, such as, for example, the mentionedfilter capacitor 80 or fixed resistor 81.

Since the output signal at output 74 of lowpass filter 75 is a signalproportional to the revolution rate, current sources 71, 72, 73 arecontrolled according to the revolution rate of the direct current motor.

The first current source 71 serves to charge a capacitor 82 which isassociated with ramp generator 21 so that a ramp-shaped voltage isgenerated across capacitor 82. By regularly discharging capacitor 82, asawtooth voltage is formed in a sawtooth generator 83. The amplitude ofthe sawtooth signal of sawtooth generator 83 is thus substantiallyindependent of the number of revolutions and the operating voltage. Withthe aid of an inverter 84, the sawtooth voltage is converted into anoppositely directed sawtooth voltage. Both sawtooth voltages, theoriginal sawtooth voltage and the inverted sawtooth voltage, feed ananalog comparison circuit 85 which supplies the respective lower one ofthe two voltages at output 86, thus producing a delta-shaped signalvoltage at output 86.

In order for the highest point of the delta voltage signal to lieapproximately in the middle between two successive commutation momentsof the direct current motor and to make this position independent of theoperating voltage, the inverting stage including inverter 84 isconnected to a fixed reference potential as indicated by a Zener diode96.

The second current source 72, controlled in proportion with therevolution rate, feeds a series connection of a series resistor 87 andthe temperature dependent resistor 51 which serves as a temperaturemeasuring sensor and may be a thermistor; its characteristics can betuned by way of series resistor 87.

The voltage drop occurring across this series connection constitutes ameasure of the momentary number of revolutions and the momentarytemperature and can be picked up at circuit point 88.

Controlled current source 73 controls a series connection composed offixed resistors 89 and 90. The voltage drop occurring across theassociated circuit point 91 is likewise associated with the momentarynumber of revolutions of the direct current motor, but contrary to thevoltage drop present at circuit point 88, it is not additionallydependent upon the temperature.

Circuit points 88, 91 are connected with the two inputs of a comparisonstage 92 which at its output 93 supplies a signal associated with therespective lower value at its two inputs. Due to the selection of therespectively lower value, the revolution rate of the direct currentmotor is not reduced further if the temperature falls below a givenlimit temperature, rather the number of revolutions is held at a fixedminimum value determined by fixed resistors 89 and 90.

The output signal of comparison stage 92 feeds the first input 94 of afurther comparison stage 95.

Further comparison stage 95 serves, on the one hand, to permit operationas a function of the revolution rate at temperatures above the lowerlimit temperature. Similarly to comparison stage 92, further comparisonstage 95 emits, at its output 97, a signal which corresponds to therespective greater one of the two input signals. As its second inputsignal, second input 98 receives the voltage drop across fixed resistor90. Further comparison stage 95 also serves to prevent further increasesin the regulating difference signal when a certain upper limittemperature is exceeded so that, even at the highest possible revolutionrate, the pulses of end stage control signal 19 have a shorter length intime than the pulses of sensor signals 5, 6 and thus it is stillpossible to control the ramps at power transistors 60, 70 and no pureswitching operation occurs in power transistors 60, 70, which would beundesirable since it would produce running noises and electricalinterferences.

Output 97 of further comparison stage 95 is connected, via a resistor99, with a comparison amplifier 101 which is connected as linearamplifier having a feedback resistor 103 which is bridged by a capacitor104 acting as attenuating element and is in communication with the firstinput 105.

The second input 106 of comparison amplifier 101 is connected, via aresistor 107, with a series connection of resistors 108, 109, 111 whichis connected with the operating voltage source. Comparison amplifier 101thus compares the voltage across the first input 105—which is limited inits limit values and is associated with the temperature and/or therevolution rate—with a voltage supplied via resistor 107 on which,however, is superposed, via a resistor 113, the delta voltage appearingat output 86.

Consequently, the output signal of comparison amplifier 101 is adelta-shaped voltage signal whose amplitude is a function of thecomparison of the voltages across inputs 105, 106. With decreasingrevolution rate and increasing temperature, respectively, the averageamplitude of the output signal of comparison amplifier 101 increases,with a delta voltage signal always being superposed on a variable directvoltage signal.

Comparison amplifier 101 acts as a revolution rate regulator whose gainis defined by resistor 99 and feedback resistor 103. The voltage droppicked up by way of resistor 107 here serves as the desired revolutionrate value on which a delta voltage is superposed to form a ramp-likeincreasing and decreasing current curve in stator windings 100, 110. Theslope of the current rise and drop, respectively, is defined essentiallyby the ratio of resistor 107 to 113.

The signal appearing at output 115 of comparison amplifier 101 isalternatingly fed, via transistors 56, 57 which act as analog switches,to power transistors 60, 70 corresponding to the time frame defined bythe commutation phases. Transistors 56, 57 then decide which one of thetwo power transistors 60, 70 receives the end stage control signal 19furnished by comparison amplifier 101. As mentioned above, this decisionis made with the aid of the output signals of comparators 54 and 55.

To ensure analog further processing of the delta-shaped end stagecontrol signals 19 of comparison amplifier 101, the already mentionedfeedback resistor 1 is provided as feedback element.

Power transistors 60, 70 have associated Zener diodes which serve tolimit the maximum turn-off voltage across power transistors 60, 70 sothat even if the ramp control of power transistors 60, 70 does notoperate, no excess turn-off voltages are generated.

Further embodiments of the invention will be described below on thebasis of the basic principles applicable to the block circuit diagramshown in FIG. 1.

The constant operating voltage V_(CC), for example a direct current of12 Volts, is present at terminals 10 and 12 of the circuit shown in FIG.3. This voltage is regulated in dependence on a variable element 20, forexample a thermistor disposed in a circuit 50 in the ventilating airstream.

A line 30 conducts the operating voltage via a diode 14 directly tostator windings 100 and 110. Outside of circuit 50, in a suitableposition with respect to the permanent magnet rotor (not shown), a Hallgenerator 260 is provided as position detector.

Circuit 50 is designed so that it can be laid out as an integratedcircuit. Two operational amplifiers 40 and 42, in conjunction with Hallgenerator 260, serves as comparators. One output 62 of Hall generator260 is connected directly with the non-inverting input 41 of comparator40 and, via a resistor 43, with the inverting input 44 of comparator 42.The antivalent output 64 of Hall generator 260 is connected in the samemanner directly with the non-inverting input 45 of comparator 42 and,via a resistor 46, with the inverting input 47 of comparator 40. Output48 of comparator 40 is connected with power transistor 70 and output 49of comparator 42 is connected with power transistor 60, with the powertransistors themselves supplying the amplifier current to stator coils100 and 110, respectively. While terminal 66 of Hall generator 260 isconnected directly with pole 12, terminal 68 is regulated via anoperational amplifier 120 in dependence on thermistor 20. A comparisonis made between a desired value and the actual value with the aid ofoperational amplifier 120 as well as with the aid of operationalamplifier 122. Depending on the voltage generated by thermistor 20 as afunction of the temperature of the stream of air in conjunction withcapacitor 22, transistors 60 and 70 are supplied in such a manner that,in the normal partial load range, they act as analog amplifier elements.Capacitor 22 prevents immediate turn-off by operational amplifier 122during start-up.

In the upper revolution rate range or near the maximum possiblerevolution rate, the revolution rate is regulated primarily by avariation of the turn-on duration of the motor current. In the lowerrevolution rate range, the revolution rate is regulated at leastadditionally by a variation of the amplitude of the motor current.Additionally, a temperature independent safety switching voltage isavailable at an output 123′ which turns off the motor after a settableperiod of time if there is an overload. Or an alarm signal can be givenif a limit value is exceeded or not reached.

As can be seen in FIG. 3, the winding ends of stator windings 100, 110on the side of the transistor are connected with diodes 167, 168 whichcouple out the voltages induced in stator windings 100, 110 so thatvoltage proportional to the revolution rate results which is fed tooperational amplifiers 120, 122 for linkage purposes. Operationalamplifier 122 serves to send an alarm to output 123′ if a limitrevolution rate is not reached. The induced voltage is filtered via RCmembers 169, 170 and integrators 171, 172, respectively, so that theripple, i.e. the alternating voltage component, of this voltage isshifted preferably by 180 degrees with respect to its fundamental wave.The thus filtered signal is superposed on the control path of Hallgenerator 260 so that the output signals of Hall generator 260 also havea ripple which is fed to amplifier stages 40, 42 and thus to powertransistors 60, 70. This causes the end stage to form current curves, ifthe motor output is reduced, which are approximately analogous to theripple of the induced voltage and contain a slight amount ofover-shooting.

While, according to FIG. 3, the type of switching and the switchingposition of transistors 60 and 70 is controlled by way of Hall generator260, FIG. 4 shows a circuit which is provided for switching andactuating transistors 60 and 70 by means of operational amplifiers 123and 125 which generate a variable signal at output 126 which is coupleddirectly to the non-inverting inputs 41 and 45 of comparators 40 and 42,respectively. If the temperatures at thermistor 20 are high, thevoltages across these inputs 41 and 45 are reduced changed to such anextent that, during the commutation phase, the “turn-on pauses pulses”in the current downstream of transistors 60 and 70 become longer.

The number of revolutions is changed in dependence on the temperature.Capacitor 22 is discharged during each commutation process and isrecharged differently by way of thermistor 20 in dependence on themeasured temperature. This voltage is present across inputs 41 and 45,respectively, via line 128 and simultaneously via diodes 130, 134 andlines 132, 136, in parallel with the voltages generated by Hallgenerator 260. As long as the voltage furnished by capacitor 22 is lessthan the voltages put out by Hall generator 260, the motor currentremains turned off. Thus a greater or smaller turn-on delay is createdin dependence on the temperature for the currents flowing through coils100 and 110, respectively. This sole turn-on delay may lead toundesirable, loud motor noises.

Therefore, FIG. 5 shows a circuit, as a modification of FIG. 3, in whichnot the pauses but the shape of the current curve between the pauses isinfluenced. This is a temperature dependent regulation of the revolutionrate in a narrower sense. A measure for the existing revolution rate thegenerator voltage of coils 100 and 110 through which no current flowsand which is applied via diodes 102 and 112, respectively, and a line114 to the inverting inputs of operational amplifiers 120 and 122,respectively. The ripple in this voltage superposed thereby serves in ananalogous manner to form rounded current curves for the currents tocoils 100 and 110 between the “pauses” which are kept short since,according to this circuit, they are not being influenced. The result isa smooth and quietly running motor compared to the embodiment of FIG. 4.In this circuit embodiment as well, the desired value for the revolutionrate is obtained via thermistor 20 in dependence on the temperature. Bymeans of an adjustable voltage divider 24, a minimum revolution rate mayadditionally be provided. Moreover, the circuit can be arranged in sucha manner that the motor can be turned off completely at a revolutionrate which is 50% below a desired revolution rate.

Moreover, an alarm signal can be put out and/or processed further atoutput 123′ if the revolution rate is too low.

FIG. 6 shows a circuit which is modified compared to FIG. 5. The shapeof the turn-on current, i.e. its rounded portions, are produced asdescribed above. The simultaneous regulation of the turn-on pauses, alsodescribed above, can additionally be given adjustable limits by way ofmembers 28 and 26 as well as 27.

FIG. 7 shows a circuit in which the power stage is influenced directlyparallel to and downstream of the Hall generator stage. Output 48 isconnected, via a transistor 69, to end stage transistor 70 and output 49is connected, via a transistor 59, to end stage transistor 60. Thesignal to change the turn-on pause for the current sent at thecorresponding temperature by thermistor 20 to coils 100 and 110,respectively, is obtained via operational amplifier 127 at its output140 and is fed to transistors 59 and 69, respectively, via respectivesemiconductor paths which produce a switching effect. The invertinginput of operational amplifier 127 is bridged forward output 140 bymeans of a low capacitance capacitor 144 and a resistor 142.

In addition, a capacitance 16 is provided which permits, via anoperational amplifier 123, an edge configuration of the current betweenturn-on pauses as will be described in greater detail below.

As can be seen from the circuit diagram of FIG. 7, in the driver circuitshown there, it is not the induced voltage which is used as a measurefor the revolution rate, but the time interval between two commutations.The rectangular pulses obtained from the Hall signal and appearing atoutputs 48, 49 of comparator stages 40, 42 are used for this purpose.They are added by way of two resistors 173, 174, with the sum signalbeing supplied via capacitor 16 to comparator 123. This comparatorbecomes temporarily conductive during each change in commutation, i.e.during each change in switching states of transistors 60 and 70, anddischarges capacitor 22 which is then able to charge itself viatemperature dependent resistor 20. Depending on the temperature, thischarging takes place faster or slower. Moreover, the charge state ofcapacitor 22 is dependent on the time duration of the charging processand thus on the revolution rate. Thus, both informations required topermit temperature dependent regulation of the revolution rate areavailable at resistor 20 and at capacitor 22. The associated signal iscompared with a voltage obtained from a fixed voltage divider and thedifference signal is fed to an operational amplifier 125. The outputsignal of the operational amplifier is filtered via a first filtermember 175, 176 and an integrator including a series resistor 177, afeedback capacitor 144 and an operational amplifier 127. Finally, thefiltered signal is fed to analog switches 59 and 69. Analog switches 59,69 additionally receive the output signal of comparator circuits 40, 42.Thus, the end stage is turned on, on the one hand, in accordance withthe output voltages of comparators 40 and 42 and, on the other hand, theturn-on duration and the maximum base current of power transistors 60,70 is influenced by the output signal of operational amplifier 127.

In this way it is accomplished that the motor current cannot be turnedon over the full turn-on duration given by Hall element 260, but isvariable in dependence on the ambient temperature detected by element20. Filtering in filter stages 175, 176 and 177, respectively, and infilter stage 144 results in the originally delta-shaped or sawtoothshaped signal at the output of operational amplifier 125 being changedto a greatly rounded signal which constitutes a favorable prerequisitefor low-noise motor operation.

While in the preceding embodiments measurement and regulation of therevolution rate as well as the determination of the shape of the currentpulse were interdependent, in the last described embodiment and in theembodiments below a pulse shape for the analog regulation phase isderived directly from components provided for this purpose. For example,a sawtooth generator including elements 118 or 119 as shown in FIG. 8 or9 can be included to generate sawtooth-shaped auxiliary signals from theturnon pulses with the aid of a capacitance, for example capacitance 16(22). The embodiment according to FIG. 8 here manages with simplecomponents and only one capacitance. It is an object of the invention tointegrate the novel circuit in a chip and it is therefore of advantageto keep the number of capacitors low. The circuit according to FIG. 9includes, like the circuit according to FIG. 8, taps 160 and 162 at theleads from output 48 to transistor 70 and from output 49 to transistor60. The pulse-shaped voltage is present via diodes 164 and 166 directlyat a transistor 119 (FIG. 8) or at a further circuit configured as shownin FIG. 9 and including an operational amplifier 118. The resultingsignal shape is present at the inverting input of operational amplifier127.

In a basic circuit shown in FIG. 10, measurement of the revolution rateby means of induced voltages is substantially separated from pulseshaping. The induced voltage is smoothed even better. However, at thesame time, the generation of a turn-on pause and of an edge ramp alongwhich analog regulation takes place are derived by means of a sawtoothgenerator. Via resistors 206 and 208, a signal voltage is available atpoint 210 which is merely interrupted in a pulsating form by the turn-onpauses. From this signal, a sawtooth signal is derived with the aid of asingle capacitor 216 downstream of transistors 212 and 214. Followingthe remaining vertical signal voltage drop at the beginning of eachswitching pause, an edge which rises linearly to the full voltage isgenerated after a pause of a self-regulating duration, and thus a rampis generated along which the analog regulation can be effected duringthe turn-on pause as a function of the signal obtained from a comparisonof the desired value with the actual value. The given values can bevaried by changing voltage source 202. The actual value is suppliedthrough output 200. The signal provided with the ramp is included in thecontrol circuit via operational amplifiers 220 and 240 in such a mannerthat it is possible to position the current pulse and set its turnofframp slope so as to avoid power losses.

As can be seen in the circuit diagram of FIG. 10, two diodes 102, 112are used again to couple out, as a measure of the revolution rate, thecounter-emf induced in stator windings 100, 110 which do not carrycurrent. The counter-emf is fed via a resistor 301 to intermediateamplifier stage 120 which acts as a lowpass filter because of capacitor144. Intermediate amplifier 120 controls controlled current source 202to charge capacitor 216, the latter being discharged at regularintervals by transistors 212 and 214. To discharge capacitor 216 it isnecessary for transistor 214 to be conductive temporarily. This iseffected with auxiliary pulses present at circuit point 210.

The auxiliary pulses are generated in the following manner. Hallgenerator 260 furnishes its voltage to two comparators 40 and 42 atwhose outputs rectangular signals appear which are shifted in phase by180° and whose high states are somewhat shorter than their low states sothat summation of these signals by means of resistors 206 and 208produces short-term low pulses at point 210 during each commutation.This causes transistor 212 to be briefly turned off and enables a basecurrent to flow for transistor 214 and a series resistor 325. A sawtoothvoltage whose amplitude is almost independent of the revolution rateappears across capacitor 216 since the loading current intensity of thiscapacitor is adapted proportionally to the time available between twocommutation pulses. The signal, proportional to the revolution rate,obtained at output 200 of amplifier 120 is supplied for a desiredvalue/actual value comparison. The voltage of a voltage dividerincluding resistors 307 and 308, which voltage is temperature dependentby way of thermistor 20, serves as the desired value. The center pointvoltage of this voltage divider is fed to the non-inverting input of anamplifier 311 and, via a series resistor 310, to the inverting input ofan amplifier 312. The respective other inputs of the amplifiers receivethe signal proportional to the revolution rate from output 200.

In this way, a potential is generated at the output of amplifier 311which grows with increasing temperature and decreasing revolution rateand at amplifier 312 a potential is generated which decreases withincreasing temperature and decreasing revolution rate. These potentialsare fed to the first inputs of amplifiers 127 and 240 at whose secondinputs the sawtooth signal of impedance converter 220 is present.

Amplifier 127 is connected as linear amplifier, for which purposeresistor 315 and resistor 142 are provided. Auxiliary capacitor 144attenuates the amplifier.

A ramp-shaped signal appears at output 140 of amplifier 127, whichsignal behaves in dependence on the temperature and on the revolutionrate in such a manner that the average potential at output 140 increaseswith increasing temperature and with decreasing revolution rate,respectively. This signal has the ramp signal of the output of impedanceconverter 220 superposed on it so that with increasing temperature andwith decreasing revolution rate, respectively, the end stage circuit iscaused to turn off later in accordance with a ramp function.

Amplifier 240 is connected as comparator. It compares the outputpotential of amplifier 312 with the sawtooth signal of sawtoothgenerator 220. A change in potential at the output of amplifier 312causes a shift in the switching point of comparator amplifier 240 in thesense that with increasing revolution rate and with decreasingtemperature, respectively, the output of amplifier 240 remains at thelow state for a longer period of time, thus keeping the end stagecircuit turned off for a longer period of time before it is able to turnon. Thus a pause proportional to the revolution rate and inverselyproportional to the temperature is introduced after the commutation.

In addition to measuring the revolution rate for regulation purposes, asecond number of revolutions measurement is made, for which comparator122 is provided. The latter has a lower voltage value as its desiredvalue which is generated by means of resistors 307 and 308, i.e. thiscomparator 122 reacts at its output 123′ if a second desired value isnot reached, which value can be set arbitrarily and serves as alarmthreshold.

The circuit as a whole has the characteristic that, in dependence ontemperature and on the momentary revolution rate, end stage transistors60, 70 are not turned on in a first time interval, i.e. the turn-on isdelayed as indicated by the temperature and the revolution ratecontroller. Then, end stage transistors 60, 70 are turned on for acertain period of time. The turn-on duration also depends on thetemperature and the revolution rate. In a third time interval, end stagetransistors 60, 70 are turned off according to a given ramp function,with end stage transistors 60, 70 being used as analog elements and afourth time interval during which the other end stage transistor is ableto turn on remains until the next commutation.

I claim:
 1. Driver circuit for a collectorless direct current motorincluding a permanent magnet rotor having at least two poles and atleast one stator winding, comprising: a driver circuit end stageconnected to the stator winding for temporarily operating as a switch, asensor for detecting a position of the rotor, said sensor producingsensor signals which are representative of a commutation phase, acontrol signal, said control signal being supplied to said drivercircuit end stage during each said commutation phase, said controlsignal causing a ramp-shaped current curve to arise as a function oftime in the stator winding, said driver circuit end state having alinkage circuit which is controlled by said control signal and by saidsensor signals of said sensor, said linkage circuit producing an endstage control signal whose duration is variable and is less than theduration of a respective one of said sensor signals, said driver circuitend stage including at least one semiconductor element which operatesduring said commutation phase for a first period of time as a switch andfor a second period of time as an analog amplifier, current in saidsemiconductor element being relatively constant during said first periodof time and changing according to a predetermined ramp function duringsaid second period of time.
 2. Driver circuit according to claim 1,wherein said linkage circuit includes switching transistors whoseswitching states are controlled by comparators which are connected withthe outputs of a Hall generator.
 3. Driver circuit according to claim 1,wherein said linkage circuit is connected with an output of a pulsewidth shaper including a comparison amplifier circuit having a firstinput which is connected to an output of a ramp generator and having asecond input which is connected with a revolution rate setting circuit.4. Driver circuit according to claim 3, a ramp generator furnishes adelta voltage as an output signal for said pulse width shaper.
 5. Drivercircuit according to claim 3, said revolution rate setting circuit isconnected with an output of a revolution rate sensor for forming aclosed control circuit.
 6. A driver circuit as claimed in claim 1,wherein a plurality of semiconductor elements are included in saiddriver circuit, each one of said plurality of semiconductor elementsoperating during a different portion of said commutation phase for arespective first period of time as a switch and for a respective secondperiod of time as an analog amplifier, current in each saidsemiconductor element being relatively constant during said first periodof time and changing according to a ramp function during said secondperiod of time.
 7. Collectorless direct current motor for driving a fan,comprising: a stator having at least one stator winding; a permanentmagnet rotor having at least two poles and being disposed in the fieldof said at least one stator winding, said at least one stator windingbeing supplied with an operating voltage by a circuit, said circuithaving a position sensing means for detecting a position of saidpermanent magnet rotor to determine a commutation phase thereof, atleast one semiconductor element supplying current to said statorwinding, a temperature sensing means for detecting temperature of an airstream drawn by the fan, and a control means for controlling said atleast one semiconductor element during said commutation phase based uponthe temperature sensed by said temperature sensing means, said at leastone semiconductor element included in said circuit being controlled bysaid control means to operate as a switch for supplying a relativelyconstant current over a part of the commutation phase and as an analogamplifier element over another part of the commutation phase, said atleast one semiconductor element, during a period of time where in areduction in revolution rate of said permanent magnet rotor occurs,operating initially as a switch and thereafter operating temporarily asan analog amplifier, current in said at least one semiconductor elementbeing reduced during said period of time according to a predeterminedramp function.
 8. A collectorless direct current motor according toclaim 7, wherein, near a maximum revolution rate of said permanentmagnet rotor, said control means regulates said revolution ratepredominantly by varying a turn-on duration of current to said at leastone stator winding during said commutation phase and, in a lowerrevolution rate range, regulating said revolution rate additionally byvarying the amplitude of the motor current.
 9. A collectorless directcurrent motor according to claim 8, wherein a temperature dependentsafety element turns off said operating voltage after a settable timeperiod upon occurrence of an overload condition.
 10. A collectorlessdirect current motor according to claim 8, further comprising a firstcomparison means for comparing a desired revolution rate value with anactual revolution rate value for regulating said revolution rate, analarm signaling means, and a second comparison means for comparing thedesired revolution rate value with the actual revolution rate value formonitoring said revolution rate with respect to a given limit value atwhich an alarm signal is initiated by said alarm signal means.
 11. Acollectorless direct current motor according to claim 10, wherein saidgiven limit value for monitoring said revolution rate is also used forinitiating a stop order.
 12. A collectorless direct current motoraccording to claim 10, further comprising a plurality of statorwindings, wherein voltage induced by said permanent magnet rotor in oneof said plurality of stator windings through which no current flows isused to measure said actual revolution rate value.
 13. A collectorlessdirect c current motor according to claim 8 further comprising a firstcomparison means for comparing a desired revolution rate value with anactual revolution rate value for regulating said revolution rate, and asecond comparison means for comparing the desired revolution rate valuewith the actual revolution rate value and initiating a stop order forcutting off the current upon reaching a given limit value.
 14. Acollectorless direct current motor according to claim 8, wherein saidcontrol means derives a signal for regulation of said revolution rate isbased upon a signal received from said temperature sensing means.
 15. Acollectorless direct current motor according to claim 14, wherein saidoperating voltage for driving said at least one stator winding is usedas a command variable for regulation of said revolution rate.
 16. Acollectorless direct current motor according to claim 14, wherein asignal derived from the temperature sensing means and said operatingvoltage are command variables for regulation of said revolution rate.17. A collectorless direct current motor according to claim 8, wherein,when said revolution rate is reduced to less than 50% of said maximumrevolution rate, a switching duration of said at least one semiconductorelement in a switch mode is reduced until said at least onesemiconductor element operates purely as said analog amplifier element.18. A collectorless direct current motor according to claim 7, whereinsaid revolution rate is controlled by varying a transition intervalbetween switch operation and subsequent analog operation of saidsemiconductor elements during said commutation phase.
 19. Acollectorless direct current motor according to claim 7, wherein, uponreduction of said revolution rate, an instant at which saidsemiconductor element is turned on is delayed with respect to a turn-ontime given by said position sensing means.
 20. A collectorless directcurrent motor according to claim 7, wherein control of motor output andrevolution rate are effected in an open control chain by an externallygiven physical value.
 21. A collectorless direct current motor accordingto claim 7, wherein control of motor output and revolution rate areeffected in a closed control circuit by an externally given physicalvalue.
 22. A collectorless direct current motor according to claim 7,wherein control of motor output and revolution rate are effected by anessentially analog circuit and necessary time functions are generated byRC members.
 23. A collectorless direct current motor according to claim7, wherein a plurality of semiconductor elements are included in saidcircuit, each one of said plurality of semiconductor elements operatingduring a different portion of said commutation phase for a respectivefirst period of time as a switch and for a respective second period oftime as an analog amplifier, current in each said semiconductor elementbeing relatively constant during said first period of time and changingaccording to a ramp function during said second period of time.
 24. Abrushless DC motor, comprising: at least one winding; a rotor positionsensing circuit that senses each commutation period of the motor; adriver circuit including a number of output stages, said driver circuitoperating in connection with said rotor position sensing circuit so asto control said output stages and vary the power applied to said atleast one winding, said driver circuit including means for feeding tosaid output stages control impulses that are switched during eachcommutation period, said driver circuit also including means for varyinga characteristic of said control impulses so as to regulate the powerapplied to said at least one winding, said means for varying includinggenerator means for producing a triangular signal responsive to saidrotor position sensing circuit, whereby the period of said triangularsignal is about the period of one commutation of the motor, said meansfor varying also including means for comparing the instantaneous valueof said triangular signal with a reference signal and for applying eachdeviation of said triangular signal from said reference signal toestablish a corresponding switching duration of all of said outputstages; and wherein each one of said output stages includes at least onesemiconductor element that operates during said commutation period for afirst period of time as a switch and for a second period of time as ananalog amplifier, and wherein current in said at least one semiconductorelement is relatively constant during said first period of time andchanging according to a predetermined ramp function during said secondperiod of time.
 25. The brushless DC motor of claim 24, wherein saidcharacteristic comprises a switching duration of said control impulses.26. The brushless DC motor of claim 24, wherein said characteristiccomprises an amplitude of said control impulses.
 27. The brushless DCmotor of claim 24, wherein said comparing means applies to said outputstages a pulse during a switching on period, wherein an increase in theduration of said pulses directly corresponds to an increase intemperature.
 28. The brushless DC motor of claim 24, wherein said drivercircuit further comprises a minimum speed setting circuit that limitsthe amount by which the pulse can become shorter during the switching onperiod when the temperature falls.
 29. The brushless DC motor of claim24, wherein said driver circuit further comprises a timing circuit,wherein said generator means for producing the triangular signal isincluded in the timing circuit.
 30. The brushless DC motor of claim 24,wherein said driver circuit further comprises command signal means forproviding a reference signal to said comparing means.
 31. The brushlessDC motor of claim 30, wherein said command signal means provides saidreference signal corresponding to a desired motor speed.
 32. Thebrushless DC motor of claim 30, wherein said command signal meansprovides said reference signal corresponding to a desired localtemperature.